For instrument navigation, most aircraft rely on a number of VHF omnirange stations (VOR) which are geographically situated throughout the world. These VOR stations transmit electronic signals in a 360.degree. direction which, when received by navigational equipment aboard the aircraft, indicate to the aircraft pilot the aircraft bearing to the station; if the aircraft is equipped with distance measuring equipment (DME) the VOR signal received by the aircraft will also indicate the distance of the aircraft to the VOR station; VOR station is also referred to as a navigational station or NAVAID. The combination of bearing and distance information allows a pilot to pinpoint his location relative to the NAVAID, and by utilizing navigational charts which show the exact geographical location of the NAVAID, the precise location of the aircraft can be determined. To display the electronic position data transmitted by the NAVAID, the pilot relies upon a VOR receiver which can be manually tuned to the discrete transmitting frequency of the particular VOR station which the pilot chooses to navigate by. The pilot then selects a particular VOR radial by manually selecting that radial at the VOR receiver. The VOR display equipment in the aircraft then displays the aircraft geographic position relative to the selected radial as well as distance from the NAVAID, information hereinafter referred to as place-bearing-distance (PBD) information. PBD data can be utilized to create navigational points to guide the aircraft along its route thereby allowing the pilot much more flexibility in planning the route of the aircraft; these place-bearing-distance navigational guidepoints are also known as "waypoints".
Many of the sophisticated aircraft navigational systems include a programmable digital flight management computer (FMC) for programming flight navigational information prior to takeoff; the flight navigational information including guidepoints and active flight plan data defining the planned route of travel of the aircraft. Also included is a control display unit (CDU) for controlling the navigational system and displaying data to the aircrew; and a horizontal situation indicator (HSI) for displaying the navigational information such as the geographic location of NAVAIDS and guidepoints on a CRT screen located in the cockpit. The HSI displays the NAVAID guidepoints and flight path legs on the CRT together with the present position of the aircraft relative to those navigational points so that the aircrew has a pictorial presentation of the aircraft's journey. The flight management computer can be coupled to the aircraft's flight control system to automatically fly the planned route.
In order to allow the computer to be programmed in flight, the cockpit is equipped with an alphanumeric keypad accessible to the aircrew. Sometimes in-flight modification of the flight path is necessary due to traffic conflicts or weather changes. The aircrew enters the desired flight path into the computer by entering the guidepoints defining the modified flight path, the flight path information is then displayed at the CDU and the geographical locations of the guidepoints are symbolically displayed at the HSI.
It is desirable that any in-flight programming by the aircrew be accomplished as quickly and as easily as possible. Present day commercial airline aircraft are now being designed for operation by two pilots instead of three, government approval of the two-pilot commercial airline aircraft based on an aircraft design which allows for safe aircraft operation by a two pilot crew.
The use of NAVAIDS in conjunction with aircraft VOR receivers to create navigational guidepoints is of itself not new.
In U.S. Pat. No. 4, 413,322--Foster, et al, there is disclosed an area navigation device which automatically establishes guidepoints along a preselected course line intersecting with any one of four cardinal radials of a VOR station.
In U.S. Pat. No. 4,220,994--Hendrickson, there is disclosed a microprocessor based system which uses geometrical relationships to assist in aircraft navigation.
In U.S. Pat. No. 2,671,621--Schuck, there is disclosed a navigation system which provides a number of nonconverging electronic guidepaths.
In U.S. Pat. No. 3,581,073--Visher, there is disclosed apparatus and methods for continuous computation of a course line from an aircraft to a destination point.
In U.S. Pat. No. 3,899,662--Kreeger, et al, there is disclosed a method and means for reducing data transmission in synthetically generated motion display systems.
In U.S. Pat. No. 3,919,529--Baker, et al, there is disclosed a radio navigation system utilizing navigational data for the generation of aircraft positional data with respect to a radio guidance transmitter system.
In U.S. Pat. No. 3,941,983 there is disclosed apparatus for combining positional data from VOR/DME radio navigation systems with data derived from an OMEGA reciver.
In U.S. Pat. No. 3,994,456--Post, et al, there is disclosed control apparatus for an aircraft navigation system which computes a predetermined curved path between two courses.
In U.S. Pat. No. 4,070,662--Narveson, there is disclosed a display generator for generating video signals at a CRT screen.
U.S. Pat. Nos. 3,899,662; 3,919,529; 3,941,983; 3,994,456; and 4,070,662 are all incorporated herein by reference in their entirety.
The following patents were disclosed in a search instituted in association with the present invention, the following patents disclosing aircraft navigational systems comprising electronic hardware adapted to create guidepoints for determining aircraft position: U.S. Pat. Nos. 3,750,942; 4,212,067; 3,803,611; 3,796,867; 3,778,601; 3,644,928; 3,621,211; 3,652,837; 3,659,291; 3,696,426; 3,486,815; 4,069,412; 3,838,427; 3,500,413; 3,831,010; 3,534,399; 3,140,391; 3,234,552; 3,696,671; and 4,283,705.
The following patent disclosing a slew control to generate guidepoints on a CRT map display unit under the control of a digital computer is assigned to the common assignee of the present invention and is disclosed for information purposes: U.S. Pat. No. 4,086,632--Lions.